The biological clock may no longer be ticking on just the woman's side of the bed.
If current research is correct, a man's baby-making alarm may start to ring not too long after a woman's chimes its final warning toll -- around age 40.
"I don't want there to be a panic, but I think it's safe to say that the father's age should be one of many factors couples should put into the equation when planning a family," says Karine Kleinhaus, MD, PhD, a researcher at Columbia University who recently spearheaded a study on paternal age and .
Over the past decade -- and particularly during the last five years -- studies have been mounting indicating that the age of the father may affect the health of the offspring in more ways than one.
Risk of Birth Defects
Associations have been made between paternal age and the risk of birth defects and developmental disorders such as and Apert's syndrome, as well as mental illnesses like . Moreover, studies conducted by Kleinhaus and colleagues at Columbia University looked at some 90,000 births and concluded the older a man is when he conceives a child, the more likely his partner is to miscarry -- even when she is young, healthy, and has no other risk factors.
Many believe this is just the beginning of what there is to learn.
"What we know now may be just the tip of the iceberg, particularly regarding birth issues we don't fully understand. We are just beginning to look at the role of a father's age. And as time goes by it's likely we are going to learn a lot more," says Jeremy Silverman, PhD, a professor of psychiatry at Mt. Sinai Medical Center in New York City, and the researcher of a study that associated paternal age with risks of autism.
Aging Dads: What Goes Wrong
Like every system in the body, experts say the male reproductive organs have not been spared the ravages of time.
"First there seems to be some clear changes that happen on a purely chemical level as a man ages. He has lower testosterone levels, lower DHEA, lower estrogen, plus higher levels of FSH and LH, which signal pretty much the same thing in men as in women -- reproductive failure," says Hackensack University embryologist Dave McCulloh, PhD, director of laboratory services at University Reproductive Associates in Hasbrouck Heights, N.J.
In a French study of nearly 2,000 men published in 2005 in the journal Fertility and Sterility, doctors concluded that even in couples undergoing IVF an aging father could figure into the pattern of failure, more than previously thought.
But it's not just the idea of making fewer babies that is of concern. The new research is also tampering with conventional fertility wisdom, which has long asserted that because new sperm is made daily, male fertility remains untouchable.
And while the notion of unending sperm production hasn't changed, some researchers now believe that as a man ages, the task of churning out that daily supply is a little like trying to make a fresh batch of macaroni in a worn-out pasta machine.
In short, while the ingredients may be fresh, the mechanism that puts it all together gets slower and works less efficiently with age. And that means far fewer perfect macaroni -- and sperm -- to show for it.
Effects of Aging
"There is definitely evidence of weaknesses in the DNA of sperm as a man ages. And this could be the result of a weakness anywhere in the sperm-making system, from the copying mechanisms necessary to turn out new sperm every day, to the natural ability of the body to correct mistakes in that copying process, or really, any step along the way; any or all could become defective as a man ages," says Kleinhaus.
While female fertility may be limited because women are born with a limited number of eggs, Kleinhaus says it's boosted by the fact that the DNA-copying process is complete at birth -- and not generally subject to mistakes along the way.
Conversely, while men may still be able to manufacture that daily supply of sperm -- regardless of age -- Kleinhaus says they remain vulnerable to bloopers, errors, and DNA foul-ups with each and every copy that's made.
"This just doesn't impact the rate of conception, we believe it can impact the health of the baby or even the health of the pregnancy itself," says Kleinhaus.
Lifestyle: Another Break in the Sperm Chain
While the aging sperm machine may be one theory, McCulloh says there is an equally strong possibility that it may not be the aging process at all that's at fault, but rather what a man does over his lifetime that matters most.
"It is very difficult to separate the effects of natural aging from environmental effects like smoking, drinking, drug use, and radiation exposure. There are a whole battery of environmental assaults that may accumulate over time, causing at least some of the reproductive issues we now attempt to link solely to age," says McCulloh.
Silverman agrees, suggesting that much the way lifestyle practices affect the health of other systems in the body, such as the heart, so too might they affect male reproduction. "The longer a man lives, the more exposure he has -- which might make a difference," says Silverman.
At least one study indicated that oxidative damage -- one type of environmental assault -- can increase chromosomal damage in sperm.
In animal research published in 2005 in the journal Fertility and Sterility, researchers found that not only was the DNA of sperm susceptible to oxidative damage, but the older the male, the more susceptible the sperm was to developing breaks in the DNA.
It is this kind of genetic upset that experts say could be behind some of the birth defects and other problems that until recently were thought to be exclusively related to the mother.
The American Society of Reproductive Medicine now recommends that sperm donors be men that are "ideally less than 40 years of age to minimize the potential hazards of aging."
What Men Can Do
While evidence seems clear that at least the possibility of a male biological clock exists, not everyone believes it comes with a fertility alarm. Indeed, some experts cling steadfastly to the notion of omnipotent and virtually indestructible sperm at any age.
"I'm not at all convinced [age is a factor]. These are not prospective studies and you cannot pick the disease state and then work backwards. You can't do it that way because you're going to come up with the wrong conclusion. You may have the observation, but you don't have the link," asserts Andrew McCullough, MD, director of sexual health and male infertility at NYU Medical Center in New York City.
He tells WebMD that until there is a study that controls for all the variables -- which may be impossible -- all we have are assumptions and no proof.
"These are observations worth noting, but to say 'Aha, this is the answer' -- well that's a real stretch," says McCullough.
Silverman comments that while the evidence may be too new to draw finite conclusions, he says the findings thus far are relevant and a portent of things to come.
"Eventually I believe we will have the research to show that when it comes to fathering a child, time isn't always on a man's side," says Silverman.
McCulloh tells WebMD, "If you don't smoke, drink in moderation, exercise daily, and eat a healthy diet, you are likely to remain healthier in general -- and that means a healthier reproductive system overall."
Protecting the Health of Sperm
Experts also say men can take additional steps to protect the health of their sperm as well as their potency, at every age. Try the following:
- Avoid steroid use. Muculloh says it's one of the most prominent causes of infertility in men.
- Control blood pressure. If you are already taking medication for and thinking about fathering a child, tell your doctor. Muculloh says certain blood pressure medications can be detrimental to sperm.
- Reduce alcohol intake, particularly in the three months prior to conceiving.
- Get adequate cardiovascular exercise. The healthier your heart is the less likely you are to develop circulatory problems linked to .
- Limit the use of a notebook computer directly on your lap, as well as other sources of high heat, including hot tubs and Jacuzzis.
- Avoid exposure to heavy metals, such as lead and cadmium, as well as radiation and toxic chemicals, including some pesticides.
Published Sept. 25, 2006.